In the past few decades, the human society rapidly developed, the modernization level was constantly improved, meanwhile, energy and environmental problems were also getting worse. The traditional fossil energy was difficult to meet the demand of industrial development, and particularly, and the problems such as global warming, three wastes and haze brought a constant threat to the human health. Therefore, it was extremely urgent to find a clean and renewable energy to replace the traditional fossil energy. As the renewable energy most widely distributed on the earth, biomass attracts more and more attention from researchers, and there are more and more reports on the preparation of high value-added platform compounds from biomass-based raw materials, so that there is a broad prospect and significance on developing and utilizing biomass energy.
As a biomass-based C5 compound, furfural is derived from agricultural byproducts such as corn, wheat and saw dust which are widely available and renewable, and therefore, the energy reserve of the human cannot be threatened if the raw materials are utilized. Furfural may be synthesized into a plurality of platform compounds including an important high value-added intermediate, namely maleic acid which may be used as a synthesis raw material of products such as resin, a coating, an additive, a plasticizer and a drug so as to be widely applied to industrial production.
However, at present, the production route of maleic acid still adopts the way of oxidizing benzene or butane at high temperature and high pressure in the industry, the traditional fossil energy derived from petroleum is still used, and reaction conditions are relatively stringent, so that great burdens are brought for both energy and economy. In recent years, it has been constantly reported that maleic acid was synthesized by using furfural as a raw material. However, the reaction conditions of preparation methods in the reports were still relatively stringent, many reactions were required to be performed at the temperature of higher than 100° C. or the pressure of larger than 2 MPa, and the used catalysts were limited to heteropolyacid and vanadium catalysts. There is a report that H3PMo12O40+Cu(NO3)2 is used as a catalytic system, furfural is catalytically oxidized at the oxygen pressure of 2 MPa, the yield of maleic acid is 49% after 14 h, although the conversion ratio of furfural is 95%, the selectivity of maleic acid is relatively low and is 52%, and the side reaction phenomenon is relatively serious. There also is a report that maleic acid is prepared by catalyzing furfural by using H3PMo12O40.xH2O alone as a catalyst in a water/organic solvent double-phase system, although the selectivity of maleic acid is improved to a certain extent after the reaction lasts for 14 h, the yield is only 35%. Both yield and selectivity of maleic acid prepared in the reports are not high, and there is a serious defect that the reaction conditions are not mild enough, the oxygen pressure is relatively high, and the reaction time is also very long, so that the energy consumption caused by reactions is greatly increased.